![]() Hdr = "BINOM(60, 1/6) with Normal Approx" The table value for Z is the value of the cumulative normal distribution at z. To get a pretty good approximation of normal curve of mediochre fit. Z is the standard normal random variable. Normal approximation to binomial distributions, but it wouldīe a pity to use standardization and printed normal tables, only Is that the so-called best-fitting normal distributionĭoes not match the binomial distribution as closely Standardization and use of printed normal tables will giveįor using a normal approximation apply here, we do not getĮven the two-place accuracy one ordinarily expects. distribution and so results have to be looked up in statistical tables. The body of most printed tables gives probabilities rounded to four places, which usually introduces no substantial error but z-values on the margins are given only to two-place accuracy, which may lead to noticeably inaccurate answers.Įxample: Scores on the ABC college admissions test are distributed according to $\mathsf(\mu=10, \sigma=2.8869).$ pnorm(8.5, 10, 2.8868) Normal Distribution A-Level Statistics Maths revision section looking at Normal. Because printed normal tables are for the standard normal distribution one must standardize in order to use them and then lose some accuracy due to rounding errors. ![]() ![]() This generation of statistics students and texts may be the last to deal with printed tables.
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